The full extent of government spying on Kim Dotcom is still unclear - with suggestions he was being snooped on from last November.

An independent lawyer - appointed by the High Court - will assist the High Court in deciding what evidence is to be handed over to Dotcom's legal team.

But it is understood there are questions about how long the surveillance went on for - with indications that internet traffic out of Dotcom's mansion was being monitored from early November.

The Government Communications Security Bureau maintains it was asked by police to find Dotcom's location on December 14 and began surveillance two days later.

But serious questions have been raised about the credibility of the organisation since the illegal spying first emerged. An internal review of files has unearthed three more possible instances of illegal spying dating back to 2009.

It also revealed Prime Minister John Key was told about the bureau's involvement in the Dotcom case at an electronic slide show briefing on February 29 and shown a photo of him.

He says he has "absolutely no memory" of the mention - and neither does bureau director Ian Fletcher. For three weeks Mr Key has insisted he first became aware of GCSB's involvement in the Dotcom operation on September 17.

Mr Key said the cover slide was a montage of 11 small images, including one of Dotcom. "They just flashed through it, I do vaguely remember the screen so I remember it being put up."

Mr Key has lashed the GCSB for its failings over the Dotcom case. The Dominion Post revealed last week that police first told them the spying may have been illegal in February but no-one briefed Mr Key.

It is understood Mr Key has now introduced more stringent procedures for when he meets the bureau.

On Monday he asked Mr Fletcher to thoroughly review its files. The scrutiny has thrown up a case in 2009 when police asked the GCSB for call-data records for a New Zealand citizen.

Two other cases in 2010 and 2011 which involved police warrants may also have been unlawful.

HOW IT UNFOLDED

The Kim Dotcom case has invoked memory loss in everyone from Prime Minister John Key to MP John Banks and top spies Ian Fletcher and Roy Ferguson. Here's a timeline to jog their memory: